Recirculation control in a washing machine

ABSTRACT

The present invention relates to a washing machine ( 7 ) and pump ( 8 ) for a washing machine ( 7 ). The pump is driven by a brushless DC motor ( 38 ). The pump can be controlled to improve the operation of the washing machine. In one aspect the invention comprises a washing machine ( 7 ) with a variable speed pump ( 8 ) for pumping out wastewater, a controller ( 50 ) for controlling the speed of the pump and a sensor ( 10 ) for determining the flow-rate of water being pumped from the washing machine, wherein the controller ( 50 ) controls the speed of the pump to maintain the flow-rate at a desirable level.

CROSS-REFERENCE AND INCORPORATION BY REFERENCE

This application claims the benefit of U.S. provisional patentapplication Ser. No. 60/748,235, entitled “Improvements Relating toWashing Machines” filed on Dec. 7, 2005, which is hereby incorporated byreference.

FIELD OF THE INVENTION

The present invention relates to improvements in the control of washingmachines. In particular, the invention relates to, although is notlimited to, the use of a brushless DC motor to drive a pump in a washingmachine, and the operation of the pump in various ways to providevarious functionality in the washing machine.

BACKGROUND TO THE INVENTION

In existing washing machines, pumps are used for recirculation anddraining of wash water. The motors typically used for such pumps provideminimal control over operation of the pump.

SUMMARY OF THE INVENTION

It is an object of the invention to provide for improved control of awashing machine pump, and/or improved features of a washing machine pumpitself.

In one aspect the present invention may be said to consist in a washingmachine adapted to drain water at a preferred flow-rate comprising: abowl adapted to hold water, a variable speed pump adapted to drain waterfrom the bowl, a sensor adapted to sense one or more parameters that canbe utilised to determine the drain flow-rate of water from the bowl, acontroller adapted determine the drain flow rate using the one or moresensed parameters and adapted to control the speed of the punp, and astore adapted to store data defining a preferred drain flow-rate,wherein the controller is adapted to control the speed of the pump todrain water at a preferred flow-rate as defined by data in the store.

Preferably the data defining a preferred drain flow-rate defines one ormore preferred flow-rates.

Preferably the data defines a range of preferred flow-rates.

Preferably the data defines a range of preferred flow-rates of 15 to 25litres per minute.

Preferably the sensor is a pressure sensor that can sense the waterpressure at multiple instants in the bowl and wherein the water pressureat an instant indicates the water level in the bowl and wherein thecontroller is adapted to calculate the drain flow-rate of water from thebowl from the change in water level in the bowl.

Preferably the sensor senses current drawn by the pump at multipleinstants and wherein the controller is adapted to calculate the drainflow-rate of water from the bowl from the change in current drawn by thepump.

Preferably the controller is adapted to control the speed of the pumpby: calculating the drain flow-rate of water from the bowl, comparingthe calculated drain flow-rate with a preferred drain flow-rate definedby data stored in the store, increasing the pump speed if the drainflow-rate is less than a preferred drain flow-rate, and decreasing thepump speed if the drain flow-rate is more than a preferred drainflow-rate.

Preferably the controller is adapted to alter the data to define a newspeed when the speed of the pump is increased or decreased.

In another aspect the present invention may be said to consist in amethod of controlling a washing machine comprising a bowl and a variablespeed pump for draining water from the bowl, the method comprising:sensing one or more parameters that can be utilised to determine thedrain flow-rate of water from the bowl, calculating the drain flow-rateof water from the bowl using the one or more sensed parameters,comparing the calculated drain flow-rate with a preferred drainflow-rate defined by stored data, increasing the pump speed using acontroller if the drain flow-rate is less than a preferred drainflow-rate, and decreasing the pump speed using a controller if the drainflow-rate is more than a preferred drain flow-rate.

Preferably the data defining a preferred drain flow-rate defines one ormore preferred flow-rates.

Preferably the data defines a range of preferred flow-rates.

Preferably the data defines a range of preferred flow-rates of 15 to 25litres per minute.

Preferably the one or more parameters are sensed at multiple instants inthe bowl using a water pressure sensor.

Preferably the one or more parameters indicate current drawn by the pumpat multiple instants.

In another aspect the present invention may be said to consist in awashing machine comprising a bowl for holding water, a bowl adapted tohold water, a spin basket nested within the bowl such that a space isdefined between an outer water of the spin basket and an inner wall ofthe bowl, a variable speed pump adapted to pump water into the bowland/or spin basket, a controller adapted to control the speed of thepump, and wherein the controller is adapted to increase the speed of thepump to pump water into the spin basket, and the controller is adaptedto decrease the speed of the pump to pump water on to the outer wall ofthe spin basket to remove debris.

Preferably the controller is adapted to increase the speed of the pumpto a first speed to pump water into the spin basket, and the controlleris adapted to decrease the speed of the pump to a second speed to pumpwater on to the outer wall of the spin basket to remove debris.

Preferably the first speed is 2000 rpm and the second speed is 1000 rpmor 600 rpm

In another aspect the present invention may be said to consist in amethod for removing debris from a spin basket of a washing machine, thespin basket being nested in a bowl, the method comprising: operating apump to pump water into the spin basket by increasing the speed of thepump, and operating the pump to pump water onto an outer wall of thespin basket to remove debris by decreasing the speed of the pump.

Preferably to pump water into the spin basket the pump is operated at afirst speed, and to pump water on to the outer wall of the spin basketto remove debris the pump is operated a second speed.

Preferably the first speed is 2000 rpm and the second speed is 1000 rpmor 600 rpm

In one aspect the present invention may be said to consist in a washingmachine comprising: a bowl adapted to hold water, an inlet with a valveadapted for connection to a water supply, the inlet and valve allowingcontrolled introduction of water into the bowl when the inlet isconnected to a water supply, a variable speed pump adapted torecirculate water within the bowl, a sensor adapted to measure one ormore parameters indicative of current drawn by the pump duringoperation, a controller adapted to control the speed of the pump and tocontrol introduction of water into the bowl by controlling the valve,and wherein the controller is adapted to: receive input from the sensorand determine pump current from the one or more parameters indicative ofcurrent, detect ventilation if the pump current is less than athreshold, and reduce the speed of or stop the pump and/or introducewater into the bowl if ventilation is detected in order to reduce theeffects of ventilation.

Preferably the threshold is a 20% reduction in pump current from areference value.

Preferably if the controller detects ventilation, the controller isadapted to:

stop the pump, increase the ventilation timer, determine a measure of apump timer value with respect to a ventilation timer value, and operatethe valve to introduce water into the bowl based on a first relationshipof the measure to a first threshold.

Preferably the controller is further adapted to: start the pump uponoperating the valve to introduce water into the bowl, increase the pumptimer, determine a measure of the pump timer value with respect to theventilation timer value, and operate the valve to prevent introductionwater into the bowl based on a second relationship of the measure to asecond threshold.

Preferably the measure is the ratio of the pump timer value to theventilation timer value, and the first relationship is the ratio of thepump timer value to ventilation timer value exceeding the firstthreshold.

Preferably second relationship is the ratio of the pump timer value toventilation timer value exceeding the second threshold.

Preferably the ventilation timer and pump timer are implemented in thecontroller.

In another aspect the present invention may be said to consist in amethod of alleviating the effects of ventilation in a washing machinecomprising a bowl adapted to hold water and a variable speed pumpadapted to recirculate water within the bowl, the method comprising:sensing one or more parameters indicative of current drawn by the pumpduring operation, determining pump current from the one or moreparameters indicative of current, detecting ventilation if the pumpcurrent is less than a threshold, and reducing the speed of or stoppingthe pump and/or introducing water into the bowl if ventilation isdetected in order to reduce the effects of ventilation.

Preferably the threshold is a 20% reduction in pump current from areference value.

Preferably the method comprises increasing a ventilation timer uponstopping the pump, determining a measure of a pump timer value withrespect to a ventilation timer value, and operating a valve in an inletcoupled to a water supply to introduce water into the bowl based on afirst relationship of the measure to a first threshold.

Preferably the method comprises starting the pump upon operating thevalve to introduce water into the bowl, increasing the pump timer,determining a measure of the pump timer value with respect to theventilation timer value, and operating the valve to prevent introductionwater into the bowl based on a second relationship of the measure to asecond threshold.

Preferably the measure is the ratio of the pump timer value to theventilation timer value, and the first relationship is the ratio of thepump timer value to ventilation timer value exceeding the firstthreshold.

Preferably second relationship is the ratio of the pump timer value toventilation timer value exceeding the second threshold.

In another aspect the present invention may be said to consist in awashing machine comprising: a pump operated by a motor, the pump adaptedto pump water within the washing machine, a sensor adapted to sense oneor more parameters of the motor that can be utilised to determine themotor speed, and a controller coupled to the sensor and the motor, thecontroller adapted to: determine the motor speed using the one or moresensed parameters, detect a blockage in the pump when the motor speedfalls below a threshold speed, and control the motor to dislodge theblockage when a blockage is detected.

Preferably the threshold speed is zero.

Preferably the motor is a stepper motor.

Preferably the controller is adapted to control the motor to dislodgethe blockage by stopping the motor and then restarting the motor byapplying a first excitation.

Preferably the controller is further adapted to: re-determine the motorspeed using the one or more sensed parameters, re-detect a blockage inthe pump if the motor speed falls below a threshold speed, and controlthe motor to dislodge the blockage by stopping the motor a second timeand restarting the motor by applying a second excitation that promotes ahigher average current to provide a higher torque than the firstexcitation.

Preferably the controller is further adapted to: re-determine the motorspeed using the one or more sensed parameters, re-detect a blockage inthe pump if the motor speed falls below a threshold speed, and controlthe motor to dislodge the blockage if a blockage is re-detected bystopping the motor a third time and stepping the motor backwards.

Preferably the controller is further adapted to control the motor todislodge the blockage by restarting the motor.

Preferably the controller is further adapted to: re-determine the motorspeed using the one or more sensed parameters, re-detect a blockage inthe pump if the motor speed falls below a threshold speed, and controlthe motor to dislodge the blockage if a blockage is re-detected bystopping the motor a fourth time and restarting the motor.

Preferably the sensor is a back emf sensor from which motor commutationrate is inferred, wherein the motor commutation rate indicates motorspeed, and wherein the controller detects a blockage in the pump whenthe motor speed falls below a threshold speed by detecting when themotor commutation rate falls below exceeds a threshold rate.

In another aspect the present invention may be said to consist in amethod for dislodging a blockage in a water pump in a washing machine,the water pump being operated by a motor, the method comprising: sensingone or more parameters of the motor that can be utilised to determinethe motor speed, determining the motor speed using the one or moresensed parameters, detecting a blockage in the pump when the motor speedfalls below a threshold speed, and controlling the motor to dislodge theblockage if a blockage is detected.

Preferably the threshold speed is zero.

Preferably the motor is a stepper motor.

Preferably controlling the motor to dislodge the blockage comprisesstopping the motor and then restarting the motor by applying a firstexcitation.

Preferably a method according to the claims further comprising:re-determining the motor speed using the one or more sensed parameters,re-detecting a blockage in the pump if the motor speed falls below athreshold speed, and controlling the motor to dislodge the blockage if ablockage is re-detected by stopping the motor a second time andrestarting the motor by applying a second excitation that promotes ahigher average current to provide a higher torque than the firstexcitation.

Preferably the method comprises re-determining the motor speed using theone or more sensed parameters, re-detecting a blockage in the pump ifthe motor speed falls below a threshold speed, and controlling the motorto dislodge the blockage if a blockage is re-detected by stopping themotor a third time and stepping the motor backwards.

Preferably the method comprises controlling the motor to dislodge theblockage by restarting the motor.

Preferably the method comprises re-determining the motor speed using theone or more sensed parameters, re-detecting a blockage in the pump ifthe motor speed falls below a threshold speed, and controlling the motorto dislodge the blockage if a blockage is re-detected by stopping themotor a fourth time and restarting the motor.

Preferably the one or more sensed parameters are motor back emf whereinthe motor back emf indicates motor commutation rate which motor speed,and wherein a blockage is detected in the pump when the motor speedfalls below a threshold speed by detecting when the motor commutationrate fall below a threshold rate.

In another aspect the present invention may be said to consist in awashing machine comprising a pump operated by a motor, a controller forcontrolling rotation of the pump, and a speed sensor for sensing speedof the pump rotor, wherein zero speed indicates a blockage in theimpeller, wherein upon detecting zero speed the controller can controlthe motor of the pump to step the motor in reverse to dislodge theblockage.

In another aspect the present invention may be said to consist in amethod of controlling a washing machine with a pump operated by a motor,the method comprising sensing the speed of the pump rotor, wherein upondetecting zero speed indicates a blockage, the method further comprisingcontrolling the motor of the pump to step the motor in reverse todislodge the blockage.

In another aspect the present invention may be said to consist in awashing machine with a bowl adapted to hold water in an interiorportion, the washing machine comprising: a pump coupled to the bowl andadapted to pump water from the bowl, the pump comprising: a housingcoupled to or integrated with the bowl, an outlet in the housing coupledto a recirculation conduit for recirculation of water to the bowlinterior, a pump actuator disposed in the housing for transferring waterto the outlet and recirculation conduit, and a conduit to provide fluidcommunication between the exterior of the housing and the outlet tosubstantially equalise water pressure such that water in therecirculation conduit does not rise above the water level in the washingmachine bowl.

Preferably the pump actuator is an impeller and the pump furthercomprises a motor arranged to rotate the impeller.

Preferably the outlet protrudes from the housing and has an outer walldefining an interior portion in fluid communication with the housing,wherein the outlet comprises an aperture in the outer wall and furthercomprising housing cover on which the conduit is disposed wherein thehousing and the housing cover are arranged such that the conduit isaligned to provide fluid communication between the interior of the bowland the interior portion of the outlet.

In another aspect the present invention may be said to consist in awashing machine pump for installation in a washing machine with a bowladapted to hold water in an interior portion, the pump being adapted tobe coupled to the bowl and to pump water from the bowl, the pumpcomprising: a housing for coupling to the bowl, an outlet in the housingadapted to be coupled to a recirculation conduit of a washing machinefor recirculation of water to the bowl interior, a pump actuatordisposed in the housing for transferring water to the outlet andrecirculation conduit, and a conduit to provide fluid communicationbetween the exterior and the outlet interior to substantially equalisepressure in the outlet with ambient pressure.

Preferably the pump actuator is an impeller and the pump furthercomprises a motor arrange to rotate the impeller.

Preferably the outlet protrudes from the housing and has an outer walldefining an interior portion in fluid communication with the housinginterior, wherein the outlet comprises an aperture in the outer wall andfurther comprising a housing cover on which the conduit is disposedwherein the housing and the housing cover are arranged such that theconduit is aligned to provide fluid communication between ambientpressure and the interior portion of the outlet.

In another aspect the present invention may be said to consist in awashing machine pump comprising a housing with a recirculation outletand a housing cover adapted for coupling to a washing machine bowl, thehousing cover comprising a conduit for providing fluid communicationbetween the housing and a washing machine bowl on which the pump isinstalled to equalise water pressure an interior portion of the bowl andan interior of the housing.

In another aspect the present invention may be said to consist in awashing machine pump comprising a housing adapted to be installed on theexterior of a washing machine bowl, the housing having a recirculationand a drain outlet, a valve disposed in the housing to alternately abutagainst and close the drain and recirculation outlets, and a housingcover adapted to be installed in a washing machine bowl, the housingcover comprising a conduit providing fluid communication between thehousing and a washing machine bowl on which the pump is installed toreduce unseating forces of the valve when abutted against therecirculation or drain outlets.

In another aspect the present invention may be said to consist in awashing machine pump comprising: a housing for coupling to the bowl of awashing machine, the housing comprising a interior for an impeller, animpeller rotatably disposed in the interior, and one or more outlets inthe housing, wherein the impeller comprises a first set of impellerblades positioned on a first surface that are adapted to transfer waterthrough the outlets upon rotation of the impeller, and the impellercomprises a second set of impeller blades positioned on a secondsurface, the second set of impeller blades being adapted to create avortex in the housing to emit debris from the impeller that is on oradjacent the second surface.

Preferably first surface is a top surface of the impeller and the secondsurface is a bottom surface of the impeller and wherein the recesscomprising a bearing and wherein the impeller rotates on a bearingadjacent the bottom surface.

Preferably the impeller is second set of impeller blades comprises oneor more elongated protrusions extending radially on the bottom surface.

In another aspect the present invention may be said to consist in awashing machine pump for a washing machine, the pump comprising arotatable impeller with vanes on the upper surface to pump water, andvanes on the underside that, during operation, produce a centrifugalaction that emits foreign objects from the impeller assembly.

In another aspect the present invention may be said to consist in awashing machine pump for installation in a washing machine with a bowladapted to hold water in an interior portion, the pump being adapted tobe coupled to the bowl and to pump water from the bowl, the pumpcomprising: a housing for coupling to the bowl such and a housing coverwith an aperture, the housing and housing cover arranged to define ahousing interior that is in fluid communication with the bowl interiorvia the aperture, and a filter for filtering water entering the housinginterior via the aperture, wherein the filter comprises a profiled wallextending from the housing cover and encircling the aperture to define avolute around the aperture, and wherein the filter comprises a hooddisposed above the wall, the hood having a perimeter, said perimeterhave a profile substantially corresponding with that of the profiledwall to allow for a profiled space between the perimeter and theprofiled wall, wherein the profiled space allows water to enter thevolute but substantially prevents elongated objects entering the volute.

Preferably the profiled wall is shaped to provide an exterior shape issubstantially non-planar in shape.

Preferably the profiled wall is shaped to provide angular portions inthe exterior shape.

Preferably the profiled wall is shaped to provide curved portions in theexterior shape.

In another aspect the present invention may be said to consist in awashing machine with a bowl adapted to hold water in an interiorportion, the washing machine comprising: a pump coupled to the bowl andadapted to pump water from the bowl, the pump comprising: a housingcoupled the bowl and a housing cover with an aperture, the housing andhousing cover arranged to define a housing interior that is in fluidcommunication with the bowl interior via the aperture, and a filter forfiltering water entering the housing interior via the aperture, whereinthe filter comprises a profiled wall extending from the housing coverand encircling the aperture to define a volute around the aperture, andwherein the filter comprises a hood disposed above the wall, the hoodhaving a perimeter, said perimeter have a profile substantiallycorresponding with that of the profiled wall to allow for a profiledspace between the perimeter and the profiled wall, wherein the profiledspace allows water from the bowl to enter the volute but substantiallyprevents elongated objects from the bowl entering the volute.

Preferably the profiled wall is shaped to provide an exterior shape issubstantially non-planar in shape.

Preferably the profiled wall is shaped to provide angular portions inthe exterior shape.

Preferably the profiled wall is shaped to provide curved portions in theexterior shape.

In another aspect the present invention may be said to consist in a pumpfor a washing machine comprising an inlet filter for filtering waterentering the pump, the filter formed from a profiled wall forming avolute around the inlet to the pump, and a hood disposed above the wall,the hood having a lip around the perimeter, said perimeter have aprofile commensurate with that of the wall, but allowing for a shapedspace between the inside of the lip and the profiled wall, such thatwater can enter the volute, but the shaped space preventing elongatedobjects entering the volute.

In one aspect the present invention may be said to consist in a washingmachine pump for installation in a washing machine with a bowl adaptedto hold water in an interior portion, the pump being adapted to becoupled to the bowl and to pump water from the bowl, the pumpcomprising: a housing for coupling to the bowl, the housing having aninterior, an impeller disposed in the interior, a motor for driving theimpeller, a housing cover comprising a first aperture for fluidcommunication to the housing interior and comprising a wall extendingfrom the housing cover and encircling the first aperture to define avolute around the first aperture, and a hood disposed above the wall,the hood comprising a second aperture for venting air bubbles.

Preferably comprising a bulb in the hood for accommodating air bubbles,wherein the second aperture is in the bulb.

Preferably the bulb is adapted to accommodate lint.

Preferably the bulb tapers from above the first aperture to a secondportion adjacent a conduit to provide for increase water flow and lowerpressure above the conduit, wherein the conduit is in fluidcommunication with a drain of the housing.

In another aspect the present invention may be said to consist in awashing machine with a bowl adapted to hold water in an interiorportion, the washing machine comprising: a housing for coupling to thebowl, the housing having an interior, an impeller disposed in theinterior, a motor for driving the impeller, a housing cover comprising afirst aperture for fluid communication between the bowl interior and thehousing interior and comprising a wall extending from the housing coverand encircling the first aperture to define a volute around the firstaperture, and a hood disposed above the wall, the hood comprising asecond aperture for venting air bubbles into the bowl interior.

Preferably a bulb in the hood for accommodating air bubbles, wherein thesecond aperture is in the bulb.

Preferably the bulb is adapted to accommodate lint.

Preferably bulb tapers from above the first aperture to a second portionadjacent a conduit to provide for increase water flow and lower pressureabove the conduit, wherein the conduit is in fluid communication with adrain of the housing.

In another aspect the present invention may be said to consist in awashing machine with a variable speed pump for pumping out wastewater, acontroller for controlling the speed of the pump and a sensor fordetermining the flow-rate of water being pumped from the washingmachine, wherein the controller controls the speed of the pump tomaintain the flow-rate at a desirable level.

In one aspect the present invention may be said to consist in a methodof controlling a washing machine with a variable speed pump for pumpingout wastewater, the method comprising determining the flow-rate of waterbeing pumped from the washing machine, and controlling the speed of thepump to maintain the flow-rate at a desirable level.

In another aspect the present invention may be said to consist in awashing machine with a variable speed pump and a pump controller,wherein the spray pattern for recirculation of water in the washingmachine can be altered by varying the pump speed using the controller.

In another aspect the present invention may be said to consist in amethod of controlling a washing machine with a variable speed pump and apump controller, the method comprising varying the pump speed using acontroller to alter the spray pattern during recirculation of water.

In another aspect the present invention may be said to consist in awashing machine with a variable speed pump for recirculating waterwithin a washing machine bowl, a controller for controlling the speed ofthe pump and introduction of water into the washing machine bowl, and asensor for determining the current in the pump stator, wherein thecontroller controls the washing machine to introduce further water intothe washing machine bowl when the current level is below a thresholdindicating that the pump is ventilating.

In another aspect the present invention may be said to consist in amethod of controlling a washing machine with a variable speed pump forrecirculating water within a washing machine bowl, the method comprisingdetermining the current in the pump stator, and controlling the washingmachine to introduce further water into the washing machine bowl whenthe current level is below a threshold indicating that the pump isventilating.

In this specification where reference has been made to patentspecifications, other external documents, or other sources ofinformation, this is generally for the purpose of providing a contextfor discussing the features of the invention. Unless specifically statedotherwise, reference to such external documents is not to be construedas an admission that such documents, or such sources of information, inany jurisdiction, are prior art, or form part of the common generalknowledge in the art

The term “comprising” as used in this specification means “consisting atleast in part of”. Related terms such as “comprise” and “comprised” areto be interpreted in the same manner.

To those skilled in the art to which the invention relates, many changesin construction and widely differing embodiments and applications of theinvention will suggest themselves without departing from the scope ofthe invention as defined in the appended claims. The disclosures and thedescriptions herein are purely illustrative and are not intended to bein any sense limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention will be described with referenceto the accompanying drawings of which:

FIG. 1 shows a washing machine with a portion cutaway to show part of awashing machine bowl and pump,

FIGS. 2 to 5 show various views of a washing machine bowl of a washingmachine, including a pump driven by a brushless DC motor arranged in thebottom of the washing machine bowl,

FIGS. 6 a and 6 b show an exploded perspective view and a cross-sectionview of the brushless DC motor pump, and

FIG. 7 shows a controller used in the washing machine to controloperation of the pump,

FIGS. 8 and 9 show flow diagrams setting out methods of adjusting thepump speed to maintain a constant drain flow-rate,

FIGS. 10 and 11 show flow diagrams of ventilation sensing andalleviation methods,

FIGS. 12 a and 12 b show flow diagrams of impeller blockage dislodgingmethods,

FIGS. 13 a to 13 c show the impeller of the pump in further detail,

FIGS. 14 a to 14 c show two embodiments of the volute wall,

FIG. 15 shows a cross-sectioned schematic diagram of the washing machinewith the pump shown and various water flow paths,

FIG. 16 shows a graph of flow-rate (litres/minute) vs current (mA) forthe pump for various pump speeds (rpm) and head heights,

FIG. 17 shows a graph of flow-rate vs speed for various head heights,and

FIG. 18 is a flow diagram showing a flushing method.

DETAILED DESCRIPTION

FIG. 1 shows a washing machine 7 in accordance with the invention,including a pump 8 that can be operated in various manners in order toimprove the operation of the washing machine. The washing machinecomprises an outer wrapper 1, a lid 2 and a control panel 3 on a frontface 4. The control panel is connected to washing machine controlelectronics, comprising a controller 50 to be described in relation toFIG. 7, and other electronics for control of the washing machine. Itwill be appreciated that the washing machine comprises a number of othercomponents that are not shown which are typical to a washing machine ofthis type and will be known to those skilled in the art. As shown in thecutaway portion the washing machine also contains a washing machine bowlor tub 6 within the outer wrapper 1. The washing machine bowl has aninterior 150 (shown in FIGS. 5, 15) for holding wash water, and also forretaining a spin basket 151 (shown schematically in FIG. 15). Referringto FIG. 15 the spin basket is nested in the bowl 6 with a tolerance suchthat the spin basket can rotate and/or move within the bowl 6. A gap 153preferably exists between the outer wall of the spin basket and innerwall of the bowl 6. The spin basket holds a wash load and is manipulatedwithin the wash bowl 6 in order to clean the items in the wash load in amanner known to those skilled in the art.

The washing machine pump 8 is provided to allow for recirculation ofwater in the wash bowl and draining of water from the wash bowl.Referring to FIG. 15, which shows aspects of the washing machine inschematic form, the washing machine also comprises a water inlet 154 andcontrol valve 155 that is adapted to be connected to a water supply. Thecontrol valve is operated by the controller 50 during various stages ofoperation of the machine 7 to introduce water into the bowl 6 forwashing the wash load in the spin basket. Details of this will be knownto those skilled in the art. Note that FIG. 15 omits details of themotor for operating the spin basket 151.

The present invention relates to various features and operations of thepump in relation to the washing machine to improve one or more aspectsof the washing machine operation. The washing machine pump 8 and itsrelationship to the washing machine bowl will be described in moredetail with respect to FIGS. 2 to 5.

The washing machine bowl 6 according to one embodiment of the inventionis shown in FIGS. 2 to 5. The washing machine bowl 6 can be assembledinto a washing machine housing cabinet or wrapper 1 as shown in FIGS. 1and 15 in the usual manner and with the usual control mechanism toprovide a washing machine appliance. The washing machine bowl 6 ispreferably moulded from a suitable plastics material as known by thoseskilled in the art. The bowl comprises a generally cylindrical shapewith external wall profiling. It also comprises an aperture 12 formounting (see FIG. 5) a rotor 13 of an electric motor (only the rotor 13is shown) for controlling the movement of the bowl 6 and spin basket 151therein during agitate and spin cycles. The motor can be any suitableknow to those skilled in the art. The washing machine bowl 6 has thewashing machine pump 8 attached to the bottom of the bowl 6. The pump isa variable speed pump 8 assembly operated by a brushless DC motor(hidden in the pump housing 20 but partially shown in FIG. 6). Thisprovides a pump mechanism for carrying out various operations during themachine's washing cycle. In brief, the brushless DC motor pump 8comprises a housing 20 that is moulded into the outer bowl 6, or boltedor otherwise fixed to the bottom of the washing machine bowl 6 (such asdescribed in co-pending application NZ 543427 also filed today, 4 Nov.2005, by the same applicant). The interior of the housing 20 is in fluidcommunication with the interior of the bowl 6 which allows for pumpingof water into and out of the interior of the bowl for example as shownby the arrows in FIG. 15. The housing 20 comprises a recess cup 23(visible in FIG. 6) for a rotor and a pump actuator, such as animpeller. A stator portion of the motor is assembled outside of the washbowl 1 around the exterior of the recess for the rotor. These featuresare not all visible in FIGS. 2 to 5 but will be described in relation toFIG. 6. Referring to FIG. 3 a, the pump comprises an outlet or port 22for connection to a drain (not shown) for draining water from theinterior of the bowl 6 upon rotation of the impeller in a firstdirection. It also comprises another outlet or port 21 connected to aconduit 11 that extends up the height of the bowl 6 and has an exitaperture which spills contents into the bowl 6. This arrangementprovides for recirculation of water, upon rotation of the impeller in asecond direction, in the bowl 6 using the pump 8 though therecirculation conduit 11 and back into the bowl 6. As will be know tothose skilled in the art, during a wash cycle, wash water in the bowl 6is pumped from the bottom of the bowl 6 and sprayed back in to ensuresufficient movement of water through the wash load. FIG. 15 shows therecirculation flows through the outlet 21.

Referring to FIGS. 2 to 5, a water level sensor 10 is provided for thewashing machine bowl 6 to determine the water level in the bowl at anyparticular time. The water level sensor 10 is preferably a pressuresensor connected to the controller 50 as shown in FIG. 7. An example ofa water level 156 is shown in FIG. 15. The pressure sensor providesoutput parameters in the form of data and/or signals that are directlyor indirectly indicative of water pressure in the bowl 6 and/or can beused to determine water pressure in the bowl 6. The pressure sensor 10and controller 50 can be operated to determine the level of water in thewashing machine bowl 6 at any instant by measuring the pressure of waterin the bowl via the pressure sensing in the sensor tube 10. The pressuresensor can take measurements of pressure continuously or periodically toobtain the water pressure parameters for use in determining waterlevels. Preferably the pressure sensor 10 is a solid state siliconpressure sensor Motorola MPXD4006. This sensor outputs a voltageproportional to water level based on the water pressure. Alternativesensors could be used such as one that detects a change in inductancewith water level and is driven by a resonant circuit where the resonantfrequency is measured to determine water level. Other possible sensorscould have switch outputs for various quantized water levels. Anysuitable sensor could be provided that provide output parameters thatdirectly or indirectly provide or can be sued to determine an indicationof water level in the bowl 6.

FIGS. 6 a, 6 b show the brushless DC motor pump 8 in more detail. Theassembly comprises a pump housing 20 moulded from plastics. The pumphousing comprises recirculation and drain outlets 21, 22 for connectionto drain (not shown) and the recirculation conduit is (shown inFIGS.—2-5, 15) in the washing machine 7. The housing 20 also comprises arotor cup, recess or cavity 23 which comprises interlocking portions 24moulded into the external surface. On the rim of the top portion of thehousing 20 are lugs 25 for receiving bolts for attaching the housing 20and other lower sub-assembly components to the bottom of the washingmachine bowl 6. A seal 26 is placed on the inside of the rim on theupper portion of the housing 20. The housing has a main chamber 65 inthe interior. A flapper valve 27 is assembled on an inside portion ofthe housing 20 to close off the drain and recirculation outlets 22, 21as required. The flapper valve 27 comprises an engagement portion orhinge 28 that interlocks with a respective recess (hidden by seal 26) inthe housing 20 between the recirculation 21 and drain 22 outlets, forlocating the valve in the housing 20. Each side 29, 30 of the flappervalve 27 is profiled to abut against the opening of the drain 22 andrecirculation 21 outlets respectively. A flap of the valve 28 a isadapted to abut against a profiled surface adjacent 29 a, 30 a to therespective outlets. The flapper valve 27 can rotate along the axis ofthe interlocking engagement portion or hinge 28 and can abut againsteither the recirculation 21 or drain 22 outlet openings to form a sealas required. When the pump operates in one rotational direction, thewater dynamics coerce the flapper valve 27 to seat against therecirculation outlet 21 and close it off, putting the machine into adrain cycle. When the pump operates in another rotational direction, thewater dynamics coerce the flapper valve 27 to seat against the drainoutlet 22 and close it off, putting the machine into a recirculationcycle.

A rotor 32 which forms part of the brushless DC motor of the pump isprovided. The rotor is made of plastics material with magnetic insertse.g. 32 a and has an axle 32 c located in the cup 23 of the housing 20.In preferred embodiment there are four magnetic inserts to form fourrotor poles. The axle sits in a cylindrical bearing insert 60 disposedin the bottom of the cup 23 abutting the axial bearing 35 c allowing therotor 32 to rotate therein. A seal 33 and rotor cap 34 is assembled overthe axle 32 c along with a washer 60 a and graphite bearing 35 a toencapsulate the rotor 32 in the cup 23. A seal insert 35 b inserted inthe aperture 34 b in the cap 34 sits around the rotor 32 axle to providea seal. Another axial bearing 35 d is provided. An aperture 34 ccontaining filter 34 d is also formed through the rotor cap 34. Attachedto the top of the rotor axle is an impeller 36 formed from plasticsmaterial. The impeller 36 comprises preferably four vanes (e.g. 36 a, 36b) that pump water when the rotor 32 is rotating in either direction.The underside of the impeller also comprises further vanes fordislodging particulate matter. The impeller will be described in furtherdetail with respect to FIGS. 13 a-13 c.

Referring now to the bottom portion of the pump 8, the motor of the pumpwill be described. A stator housing 37 is assembled over the pumphousing cup 23. The stator housing 37 comprises an aperture 37 a withrecesses e.g. 37 b disposed about the circumference that interlock withthe moulded interlocking portions e.g. 24 on the exterior of the housingcup 23. This retains the stator housing 37 in place such that it isprevented from rotating. The stator housing 37 has a generally hexagonalexterior and interior although has a shaped exterior moulded to fit theshape of the stator windings and other components assembled in thehousing 20. A stator 38 is inserted inside the stator housing 37 and isretained in place by screws 56 a to 56 c or other affixing means. Thestator 38 is formed from a generally hexagonal frame 39 and a number ofstators (e.g. 40 a, 40 b, 40 c—the other stators are hidden) thatprotrude radially inwards from the frame 39. The stators 40 a-40 c areformed from stator windings in the usual manner. In one possibleembodiment, there are 6 stators. Each stator e.g. 40 a-40 c is formedfrom a coiled winding and the stators are arranged to abut closely tothe exterior of the cup 23 and arranged within the exterior interlockingmouldings 24. The stators e.g. 40 a-40 c are wired with three separatephases to provide stepped motor control. A housing base cap 41 is placedover the stator 38. The base cap 41 is held or retained in place withscrews 56 a-56 c or other affixing means. A brushless DC motorimplements electronic commutation. The pump comprises all the necessaryelectronics and software to implement the electronic commutation,including hall effect sensors and/or back emf sensors as required.Details of the commutation of brushless DC motors and how this isimplemented will be known to those skilled in the art and need not bedescribed here.

Referring now to the top portion of the pump assembly in FIG. 6, a pumpor housing cap 42 is affixed over the top opening of the housing 20 fromthe inside of the washing bowl 6. The outer perimeter of the cap 42comprises a co-moulded seal and openings 42 a, 42 b for bolts 56 d, 56 eto affix the cap to the housing 20. The top of the cap 42 comprises aflower shaped wall 43 that forms a volute 43 b on the top of the cap 42.In the volute has an opening 43 a that is coaxial with the axis of therotor 23 and entire pump assembly and sits over an aperture in thebottom of the washing bowl 6 (not shown). The opening 43 a includes acylindrical wall 43 f that extends some way up the height of the volute.Over the top of the volute is a hood 45 which has a flower shapedexterior corresponding to that of the volute wall 43. The flower shapedexterior lip 49 extends down below the top of the corresponding cap, theflower shaped wall forming the first inlet weir. The hood 45 comprisestwo lugs 46 a, 46 b which correspond to openings 42 a, 42 b in the pumpcap 42. The volute hood 45 includes a profiled bulb 47 in the topsurface. An aperture 48 in the top of the profiled bulb 47 is alsoprovided which encourages the release of air bubbles during,particularly, ventilation. The aperture 48 is of a suitable size to ventbubbles, such as between 2.5 mm to 3.5 mm in diameter. Additionally thisaperture is flushed by the water in the drain/recirculation conduitanytime the pump direction changes. A leak flow recirculation tube 43 dor conduit is also in the pump cap 42, which forms a fluid communicationchannel between the pump housing 20 and the exterior of the pump 8. Thebulb is positioned in the hood 45 such that when the hood is fittedabove the volute wall 43 the bulb extends from the aperture 43 a to theinterior of the pump to the top of the leak flow tube 43 d outlet.Preferably, the bulb is rounded at both ends and has a diameter and theaperture 43 a end that is commensurate with the diameter of the aperture43 a. This means the diameters are of a similar size, although notnecessarily exactly the same. Similarly the diameter of the bulb at theleak flow tube 43 d end is commensurate with the diameter of the leakflow tube 43 d. Preferably, therefore, the width of the bulb tapers fromthe aperture 43 a end to the leak flow tube 43 d end. This arrangementand configuration of the bulb 47 coerces water that exits the aperture43 a into the bulb portion and then directs it towards and over the endof the leak flow tube 43 d. The tapering increases the speed of thiswater flow as it tends towards the top of the leak flow tube, thuslowering the water pressure above the leak flow tube.

The purnp 8 is installed in or integrated with the bowl as shown inFIGS. 2 to 5, 6 b and 15 as described, for example, in NZ 543427.Referring to FIG. 6 b, the lower housing sub-assembly 20 is installed onthe underside of the bowl bottom 6 a, and extends below the bowl bottom6 a. The upper sub-assembly, including the cap 42 and hood 45 arepositioned in the interior of the bowl 6 above the bowl bottom 6 a. Thecap 42 is attached to the lower assembly to define a housing interior.This interior comprises the main chamber 65 that comprises among otherthings the impeller, and also the cavity for the rotor. The cap 42 andhood 45 are in fluid communication with the interior of the bowl 6 andthe cap and hood are in fluid communication with at least a portion ofthe housing interior e.g. 65 such that at least a portion of the housinginterior is in fluid communication with the bowl 6. Water enters themain chamber from the bowl 6 as shown by the arrow 144 in FIG. 15. Itcan be pumped through the recirculation output 21 and drain outlet 22(hidden behind the drain outlet 22 in FIG. 15) as required by theimpeller. When the impeller rotates in a clockwise manner when viewingthe pump from above, water that flows from the bowl 6 into the mainchamber will be transferred to the drain outlet 21 under rotation of theimpeller. When the impeller rotates in a counter-clockwise manner, waterthat flows from the bowl into the main chamber will be transferred tothe recirculation outlet 21 under rotation of the impeller and throughthe recirculation conduit 11 as shown in FIG. 15.

Referring to FIG. 7, a controller 50 is provided to control operation ofthe pump 6 and other aspects of the machine operation. The controllerforms part of the overall electronics implemented in the machine tocontrol operation. The general nature of such electronics will be knownto those skilled in the art. The CPU could be any suitablemicrocontroller, microprocessor or other controller device known tothose skilled in the art. The memory could be internal or external tothe CPU, and could be of any suitable type. There might be severaldifferent types of memory, all implemented in physically separateportions of the controller. The controller 50 also comprises water levelsensor circuitry that receives parameters in the form of signals or datafrom the water level sensor 10, be it a pressure sensor or other sensortype as described previously. The level sensor circuitry can receive thesignals or data and from this determine water pressure and/or waterlevel, or process the data or signals for passing on to the memory andCPU 51, which can carry out the processing to determine or calculatewater levels and flow-rate. For example, this can be the flow-rate fromwater in the bowl 6 out through the drain and/or recirculation outlets.By calculating the change in water level in the bowl (through waterpressure or otherwise) the CPU can determine the flow of water from thebowl and from this infer the flow-rate of water into the drain outlet22, and/or recirculation outlet 21.

The current sensors 54 are coupled to the motor of the pump 8 in orderto determine the current drawn or other parameters indicating currentfrom the pump and from this pass signals or data onto the CPU so thepump speed can be determined from the sensed current. Optionally, othersensors that sense other motor parameters could be used to determinepump speed. The controller also comprises a pump motor controller 55.The CPU 51 is coupled to this for controlling operation of the pump,such as pump speed, and starting and stopping the pumping operation. TheCPU and memory 51 are also connected to the user interface 3 forallowing operation in response to user input, and to provide output tothe user. A valve inlet controller is provided for controlling the flowof water into the bowl 6 from the water supply. Details of this will beknown to those skilled in the art.

It will be appreciated that FIG. 7 shows the logical configuration ofthe various components. The actual physical configuration could beprovided in the number of forms. For example, a number of the componentsshown could be operated in a microcontroller, microprocessor or thelike, or there could be a separate microcontroller and separatecircuitry. Those skilled in the art will appreciate that there are arange of ways to implement the functionality.

The brushless DC motor pump 8 can be operated in a number of ways toprovide various functionality in the washing machine cycle as will nowbe described.

The CPU and memory 51 in the controller implement an adaptive algorithmto maintain and adjust pump-out rates for various drain head heightinstallations during the drain cycle. The drain head height variesdepending on the location of the machine. For example, in some countriesit is conmon for the washing machine to be placed in a basement.Therefore the drain pipe has to extend vertically to empty into a drainusually above the washing machine at street level. This thereforerequires a higher pump speed to ensure sufficient water pressure toreach the required height at the desired flow-rate. In other countriesit is common to have the washing machine at floor level which can drainthrough the usual drain outlets provided at floor level. Therefore thewater pressure to keep the desired pump-out rate (flow-rate) for thedrain is less as the drain water does not have to be pumped upwardsfirst.

Therefore, in one embodiment of the invention the pump 8 speed (rpm) isaltered as required to keep the drain pump-out rate constant orsubstantially constant, irrespective of the required height to which thedrain water needs to be pumped. The method is shown generally in FIG. 8.To do so, the CPU 51 receives information from the water level sensorcircuitry 53 to determine the level of water, step 70, 71, at anyparticular time. The water level sensor circuitry 53 is connected to thewater level sensor 10 in the bowl 6, which together determine the waterlevel from the pressure. By monitoring the change in water level throughthe level sensor 10 the CPU 51 can calculate the flow-rate of drainwater out of the washing machine bowl 6. If the drain flow-rate dropsbelow a desirable level, step 72, for example due to a high head heightfor the drain pipe, then the CPU 51 can increase the pump speed, step74, by way of the motor controller 55. Alternatively, if the pump outrate is greater than the required level, then the CPU 51 can slow downthe pump, step 73, by way of the motor controller 55. Preferably thedrain of the flow rate is in the order of 17 to 20 litres per minute,although it will be appreciated by those skilled in the art that thiswill alter in various circumstances. At a 4 foot head height, thistranslates into a pump speed of approximately 2400 rpm. At 6 foot and 8foot this translates into pump speeds of approximately 2900 rpm and 3300rpm respectively.

It will be appreciated that these figures are indicative only and actualvalues will depend on head height and pump characteristics. The benefitof altering the flow-rate is that the speed of the pump can be reducedto the minimum speed required, thus reducing unnecessary noise, andenergy consumption. It will be appreciated that the flow rate could bekept to with any suitable preferred flow-rate range, or alternatively aspecific flow-rate. In this specification, the term “preferredflow-rate” relates to either a specific flow-rate, or a preferredflow-rate range which encompasses some tolerance. The preferredflow-rate is defined by data stored in memory 51.

A more detailed description of the method will now be described with thereference to FIG. 9. During operation the controller controls the pumpby starting it at a speed as stored in memory, step 90. This will be anominal starting rpm for the motor and pump 8 that has beenpredetermined as suitable. This value can be defined by data stored inthe memory 51 or another suitable part of the controller 50. This could,for example be, an E² PROM. Throughout the process, the controller 50monitors the water level using readings from the water pressure sensorwhich sensors parameters as described previously. If the water level isbelow a threshold such that it is considered that the bowl is empty,step 91, the controller saves the current pump RPM to the memory 51 andthen controls the motor via the motor controller 55 to stop the pump andend the drain cycle, step 97. The threshold is defined by data stored inmemory 51 or other memory in the controller 50. This water level might,for example, be 50 mm of water in the bottom of the bowl, although itwill be appreciated that a suitable level might be different dependingon the characteristics of the washing machine 7. If the water level isnot yet below the empty threshold, the controller then determineswhether a reliable measure of the water level change, which correlatesto drain flow-rate, has been established, step 92. For example, themeasure might be determined as reliable if a minimum number of samplesor counts of the water level have been taken within a predeterminedtime. An example of this is if three water levels have been taken, andthis has occurred within 20 seconds. If a suitable number of readingshave not be taken in the period determined, the operation times out andthe measure is considered unreliable. If a reliable measure is notobtained, the controller continues to monitor the change in water leveluntil it obtains a reliable measure of the water level change andtherefore flow-rate, step 91. If a reliable flow-rate measure has beenobtained, the controller 50 then determines whether the drain-rate istoo slow, step 93. As described previously, it does this by comparingthe flow-rate determined with the preferred flow-rate stored in memory.Preferably, the preferred flow-rate is define by data stored in thememory 51 or other suitable memory, and this can be predetermined andset during manufacture of the machine, or configured by a technician ata later stage. Also as mentioned previously, the preferred flow-ratecould be a range of flow rates, such as preferably 15-25 litres perminute, or more preferably 17-20 litres per minute, or a more specificflow-rate if a tolerance range is not required.

If the drain flow-rate is too slow, step 93, then the CPU 51 operatesthe motor controller 55 to increase the pump speed. It increases thepump speed in proportion to the flow-rate, step 94. If the drainflow-rate is not too slow, then the CPU 51 determines if the drain rateis too fast, step 95, by comparing it to the preferred drain flow-rate.If the drain flow-rate is not too slow, then the CPU 51 goes back tomonitoring the water level using the sensor. If the drain flow-rate istoo fast then the CPU 51 controls the motor controller 55 to control thespeed of the pump. This is altered in proportion to the water levelchange, step 96. After this the CPU 51 continues monitoring the waterlevel.

As noted above, the speed of the pump is altered proportionally to thedetected water level change. For example, if the detected flow-rate is aspecified percentage (e.g. 10%) less than the preferred flow-rate, thenthe pump speed could be increased by that percentage (e.g. 10%). This isan iterative approach whereby the flow-rate is re-calculated, thepercentage difference from the preferred flow-rate determined and thespeed of the pump is altered again by the re-determined percentage. Thisiterative process continues.

Alternatively, the current drawn by the motor of the current can be usedto determine water level, instead of using the water level sensor. Ahigher water level requires less pump work or speed in order to maintaina particular flow-rate. This in turn requires the motor of the pump todraw less current. FIGS. 16 and 17 show a graph of possible flow-ratesvs current drawn by the pump motor for various motor speeds (rpm). Fromthis relationship, by measuring the pump current, the flow rate can beinferred, and then the pump speed altered accordingly to maintain thedesired flow-rate, as described in relation to FIGS. 8 and 9.

As noted in FIGS. 16 and 17, the flow rate vs. current relationships arestated for different pump speeds. The pump speed can be determined inany suitable manner. In one possibility the flow-rate is determined fromcommutation rate of the brushless DC motor. As known to those skilled inthe art, a brushless DC motor has electronic commutation. The softwareand/or electronics that operate the commutation of the excitationapplied to the coils. By using hall sensors or sensing back emf in theunenergised coils, the position of the rotor can be determined, and fromthis the rate of commutation and/or the speed of the rotor determined.This correlates to the speed of the pump. From this, the relationshipbetween speed, flow-rate and current (such as that shown in FIGS. 16 and17) is used to determine the flow-rate.

Note that FIGS. 16 and 17 show an exemplary relationship determinedexperimentally from a pump. The relationship between pump speed, motorcurrent and flow-rate will alter for pumps with differentcharacteristics. Relationships for other pumps could be determinedexperimentally and the results used as described above.

The adaptive algorithm to maintain and adjust pump-out rate can also beused to overcome partial blockages that may be present in the drainoutlet. Any partial blockages that slow the flow-rate out the drainoutlet will be detected as a slower flow-rate by the CPU 51 via thelevel sensor 10. The CPU 51 will use the motor controller 53 to alterthe pump speed so that the flow-rate reaches the desired level. Theprocess as described above will provide compensation for partialblockages when implemented. That is, the method will alleviate thedrawback of differing head heights as well as partial blockages. Themethod does not necessarily identify what is causing the change inflow-rate (be it the head height or a blockage), but rather detect theflow-rate change and alter the pump speed accordingly.

In another possible embodiment the CPU detects when too much foam hasbeen produced in the recirculation cycle. Upon detecting this, the CPU51 controls the pump by way of the motor controller 55 to slow the speedof the recirculation water. When foaming has reduced, the CPU cancontrol the pump to increase pump speed again as required. In anotherpossible embodiment of the invention, the CPU 51 can control the motorto vary the pump speed to alter the spray pattern in the washing bowl 6.Referring to FIG. 15, this shows a cross-section of the washing machinebowl 6 and the spin basket 151. The pump 8 recirculates water from thebowl through the recirculation tube 11 and back into the interior 150 ofthe bowl 6 to recirculate wash water. In a first mode the pump operatesat a standard speed which sprays the recirculation water back into thebowl as shown by the dotted line representing water spray indicated atpoint A. In an alternative mode, the pump speed can be lowered to suchthat the recirculation water does not have sufficient momentum to reachthe inner bowl but rather dribbles out the outlet of the recirculationconduit 10 and trickles down the outside of the spin basket as shown bythe dotted line representing water trickle at point B. This cleans lintand other debris off the side of the outer wall of the spin basket. Thewater still trickles within the inner wall of the bowl 6 in the gap 153between the inner wall of the bowl and the outer wall of the spinbasket. This lint flushing preferably occurs after every spin cycle.

The controller 50 can operate the motor via the motor controller 55 tooperate the pump in this manner. The controller can switch to thetrickle mode at any suitable point, such as after or during a agitateand/or drain cycle. This will be determined by preconfigured programmingof the CPU 51 and the controller 50. In one possible embodiment, thespeed of the pump for normal recirculation is 2,000 rpm while the speedfor the trickle recirculation output is 1,000 rpm. Clearly, other motorspeeds might be implemented depending on the particular characteristicsof the washing machine and the pump, such as 600 rpm for the trickleoutput.

In another possible embodiment of the invention, ventilation sensingoccurs during the recirculation cycle. Ventilation occurs when thereisn't sufficient water in the pump resulting in the pump pumpingpredominantly air. Action can be taken to alleviate ventilation whichcan economise on recirculation water volume and/or increase soapconcentration and/or reduce unnecessary noise. Recirculation occurs whenthe controller operates the pump 8 to pump water from the bowl 6 throughthe recirculation outlet 21 up the recirculation conduit 11 and up backinto the bowl. The method of ventilation sensing is generally shown inFIG. 10. The CPU 51 determines whether or not the pump is ventilating bymonitoring, step 80, the current required to turn the impeller. Thecurrent is sensed by a current sensor on the pump motor. Once thecurrent drops below a certain predetermined threshold, this indicatesthe impeller is rotating in air, not water, i.e. it is ventilating, step81. The CPU 51 will confirm low water level in the bowl 6 bycommunicating with the water level sensor 10 and level sensor circuitry53 and using the signals/data therefrom to determine/calculate waterlevel. When the water level drops to a level such that ventilationoccurs, the CPU 51 will control the washing machine 7 to introduceadditional water, step 82, into the cycle for recirculation. This isdone by the CPU operating the valve inlet controller to operate thevalve of the water supply inlet. Only a sufficient amount of water willbe introduced to prevent ventilation therefore minimising the volume ofwater required. Ventilation sensing allows the reduction of therecirculation water volume for a given wash load size and absorbency.That is, a level of ventilation can be lived with in order to allow timefor the water to drain through the clothes load before entering thepump.

The algorithm for detecting pump ventilation and altering the pumpaction in response will be described in further detail with reference tothe flow chart in FIG. 11. The controller 50 operates the water inletvalve 155 to fill the bowl to the recirculation level e.g. 156, whichwill be a water level suitable for washing or cleaning a wash load, step110. Once filled, the pump is operated by the controller to effectrecirculation, namely where water is recirculated from the bottom of thebowl through the recirculation outlet 21 up the conduit 11 and issprayed back into the bowl to provide for water recirculation. Once thisprocess begins, the controller starts a pump timer. The pump timer isimplemented in the CPU 51 or any other suitable part of the controller.A ventilation timer is also implemented to determine how long the pumpis in a ventilation mode or stage. Initially the pump timer and theventilation timer will have a zero value. The pump timer is used totrack the length of time that the pump is operating for, step 110.During the pumping and recirculation operation, the CPU 51 monitors thecurrent drawn by the motor using the current sensor 54 outputs whichprovide parameters in the form of signals/data that directly or indirectindicate motor current based on sensed current. Current monitoringprovides an indication of whether the ventilation is occurring or not.In step 111, the CPU 51 detects when the pump current has dropped tobelow a preferred (pump stop) threshold. For example, in a preferredembodiment a normal operating pump current will be defined by datastored in memory in a suitable manner. This could, for example, be oneof the operating currents shown in FIGS. 16 and 17, where a suitablenominal/normal operating current is decided based on the pump speed forthe required flow-rates. When the pump current drops below this value bya certain threshold the CPU 51 will detect that ventilation hasoccurred. For example, referring to FIGS. 16 and 17, in one embodiment,the preferred minimum flow rate might be 10 litres per minute. The pumpspeed required to achieve this could be determined based on the knownhead height of the recirculation tube. The nominal motor current drawnfor this pump speed is then determined from the relationship, forexample it might be 350 mA. At 10 litres per minute, it has beendetermined that a significant drop off of nominal current occurs whenthe pump begins ventilating, i.e. when it starts pumping predominantlyair. When this drop off in current occurs, the CPU 51 determines thatventilation has occurred. The drop off in current can be as much as20%-30%. Therefore, the CPU 51 uses this as the step down threshold. Itwould be appreciated that the 20%-30% value is one possible that couldbe used, and any suitable current threshold that could be applied inorder to determine when ventilation occurs, based on the characteristicsof the pump used and experimentation

If the pump current has not dropped below the threshold, the CPU 51operates the pump in the usual manner and determines a pump time toventilation time ratio, step 117. The pump time and ventilation timeprovide respective pump time values and ventilation time values. Thesevalues reflect the incremental time counted by the respective timers.The ratio can be detennined from these values. The pump time toventilation time ratio relates to the quantity of time the pump has beenin a pumping mode to the quantity of time that the pump has been in aventilation mode, step 117. When this ratio exceeds a secondpredetermined (stop water flow) value or threshold it will be determinedthat sufficient pumping has occurred in relation to ventilation andtherefore no further water is required in the bowl 6 for the moment. TheCPU 51 then operates the valves 155 for the water inlet 154 to preventfurther water entering the bowl 6 for the present time. The processcontinues by the CPU 51 implementing the step 111 again and monitoringthe pump current.

If the pump current does fall below the threshold, step 112, the CPU 51then temporarily stops pump operation. The CPU has determined that theventilation is occurring. It also stops the pump timer and commences theventilation timer. It then waits a preferred length of time, in thiscase 10 seconds (although other wait times could be implemented), step113. The CPU, in step 114, then determines the pump time to ventilationtime ratio and determines if this exceeds a first (start water flow)predetermined value or threshold as defined by data stored in memory. Ifit has, this indicates that too much ventilation has occurred and thereis not sufficient water in the bowl to continue the recirculationprocess. The CPU 51 then operates the valves 155 on the water supplyinlet 154, step 115, to introduce further water into the bowl 6. The CPUthen continues the recirculation process by turning the pump back oninto its usual mode to continue recirculation. It also stops theventilation timer and recommences the pump timer, step 116.

In step 114, if the pump time vs. ventilation time ratio is less than apredetermined threshold or value, indicating that the level ofventilation is not considered problematic, the CPU 51 will implementdirectly step 116 and turn the pump back on and stop the ventilationtimer and accumulate the pump timer. In this case the process oftemporarily stopping the pump is sufficient for alleviating the effectsof ventilation to a sufficient degree. At this point the CPU continueswith step 111 and monitors the pump current for the remainder of therecirculation process.

The pump timer to ventilation timer ratio threshold can be determinedbased on expected performance of the machine. In one possibility, a 50%duty cycle (or pumping time to ventilation time) might be acceptable. Inthis case, the start water flow threshold ratio might be set at 50%.This means the ventilation time (i.e. when the pump stops pumping) couldbe up to 50% before the CPU is programmed to introduce more water toprevent ventilation. This means the pumping time of a wash cycle mightonly be 50%, which would double the length of the wash cycle. Any othersuitable duty cycle could be predetermined, based on what is acceptableto the user. Where the duty cycle (i.e. pump time to ventilation time)is less, this increases the wash cycle time; however, it reduces theamount of additional water introduced. Waiting longer allows time forwater to drain through clothes in the wash load back into the pump—whichstops ventilation occurring. Conversely, where the duty cycle is more,more water will need to be introduced to prevent ventilation, as waterwill be introduced sooner. The addition of water speeds up the drainingof water through the clothes back into the pump. The decision of whereto set the duty cycle ratio is based on an acceptable compromise betweenwater usage and wash cycle time.

It will be appreciated that in determining whether action is required tobe taken, other alternatives to determining a pump time to ventilationtime ratio and comparing this to a threshold could be used. For example,a ventilation to pump time ratio could be used. Other measures arepossible. The CPU can implement any technique that determines a measureof a pump timer value with respect to a ventilation timer value and thencompares this to a threshold. This might include the measure beinghigher or lower than a threshold. Alternatively to determining whetherthe measure exceeds or falls below a threshold, the CPU might determinesome other relationship between the measure and a threshold to determineif action is required.

In the case of the example above, the ratio of the pump value timer tothe ventilation timer value is the measure, and the relationship of thisto the first (start water flow) threshold is whether or not this exceedsthe first (start water flow) threshold. Similarly the relationship ofthis measure to the second (stop water flow) threshold is whether or notthis measure exceeds the second (stop water flow) threshold.

Ventilation sensing can also occur during drain cycle to minimise pumpnoise. The method is the same as that for recirculation ventilationsensing, although it will be briefly described here. The pump current ismonitored when running and if a current reduction is noted (say morethan 20%), within a short time frame the rpm of the pump is ramped downto zero in order to stop ventilation noise and to avoid the drain gurgleassociated with an immediate pump shut off. After ten seconds or someother suitable period the pump is turned back on and the current isanalysed again in order to detect the reduction indicative ofventilation.

In another possible embodiment the motor can be controlled to provide amini-flush to drain of water, to remove the highly soiled residual waterfrom the washing machine bowl 1 left over in the bowl after drain andspin cycles. The residual water includes lint, dye and detergent.Referring to FIG. 18 to do so, the CPU 51 monitors the cycle, step 180.When the recirculation cycle starts, step 181, and some fresh water hasbeen introduced into the wash bowl 1 for recirculation, the CPU 51momentarily operates, step 182, the motor via the motor controller 55 toquickly reverse the direction of the rotor. This rotates the impellers36 in the opposite direction changing the direction in which the wateris pumped. This change in direction operates the flapper valve 27 toclose off the recirculation outlet 22 leaving the drain outlet open suchthat the soiled water is allowed to drain through this outlet 22. Aftera short time after a small amount of highly soiled water has beendrained the CPU 51 operates the motor controller 55 to change thedirection of the motor again to begin recirculation, step 183. Thischange in direction causes the impeller 36 to change direction and theassociated water dynamics forces the flapper valve 27 to abut againstand close off the drain outlet 22 and reopen the recirculation outlet21.

At the end of draining, dirty water can remain in the recirculationconduit 11 which might result in recirculation of dirty water in thenext recirculation cycle. In another possible embodiment of theinvention, is to operate the pump to drain the bowl 6 and continue thedrain pump for a period after wash water for recirculation is introducedin order to purge out the dirty water held in the recirculation conduit11. The length of time to continue pump operation would be determinedfrom conduit head height, and motor parameters to determine how long isneeded to clear the recirculation conduit 11.

In another possible embodiment of the invention, the impeller 36 can becontrolled to assist in dislodging jams or blockages in the pump 8. Whensome type of particle is lodged in the impeller 36 or between theimpeller and rotor cap 34, the motor speed will drop to or close tozero. Referring to FIG. 12 a the CPU 51 can detect this drop in speedvia the current sensor 54, step 100, and infer that some type of jam orblockage has occurred. The pump speed detection has been describedpreviously and does not require further explanation here. The CPU 51will then invoke a blockage dislodging progran, step 102, which controlsthe pump motor via the motor controller 55 to dislodge the blockage. Onesuch program could be to step the motor backwards by controlledapplication of current to sequential stators e.g. 40 a-40 c in thestator 38. Reversing the rotor 32 in this stepped manner could dislodgethe blockage. The speed and number of steps can be controlled asrequired. After stepping the rotor in reverse the CPU 51 can control themotor to rotate in a forward direction again, step 103, and monitor thecurrent sensors 54 to determine whether the motor speed has resumed to anormal level, thus indicating that the blockage has been dislodged.

In another alternative, the pump speed is determined from commutationrate of the brushless DC motor. As known to those skilled in the art, abrushless DC motor has electronic commutation. The software and/orelectronics that operate the commutation of the excitation applied tothe coils. As described earlier, by using hall sensors or sensing backemf in the unenergised coils, the position of the rotor can bedetermined, and from this the rate of commutation and/or the speed ofthe rotor determined. This correlates to the speed of the pump.

A particular example of an operation in response to the detection of ablockage will be described with reference to FIG. 12 b. The controllerstarts the pump to carry out an operation of the washing machine 7 inthe usual manner, step 120. The controller monitors the speed of themotor of the pump by calculating the speed from output from commutationrate. Other techniques could be envisaged by those skilled in the art.The CPU 51 determines if the pump speed as measured by the commutationrate has dropped below a threshold. For example, this threshold might bezero, or some other preferred threshold. For example, a speed slightlyabove zero could be specified in case there is a blockage that has notcompletely ceased impeller movement. The threshold is defined by datastored in memory 51 or elsewhere. If the pump speed has not droppedbelow the threshold, step 121, then the pump continues in the normalmanner. However, if the pump speed has dropped below the threshold thenthe controller stops operation of the pump and then restarts pump in theusual manner, step 122. For example this is by controlling the motorcontroller 17 to apply an excitation voltage to the motor of the pump,the voltage being the usual voltage for starting the pump. This is anexcitation voltage that promotes normal average current in the motor toprovide a normal starting torque. The excitation voltage is anyenergisation that is used to operate the motor, such as a Pulse WidthModulation voltage. In many instances, this operation will be sufficientto dislodge the debris or blockage and continue the pump in the usualmanner.

The CPU 51 then monitors the pump speed again after restarting the pump,step 123, and determines if the pump speed is still below the threshold.If it is not then this indicates the pump is operating normally andoperation continues as normal. However, if the CPU 51 determines thatpump speed has dropped below the threshold then the CPU stops the pumpagain. It then restarts the pump more vigorously. Preferably, this is bycontrolling the motor controller to apply a higher excitation voltagerequired than normal for starting the pump, step 124. This is anexcitation voltage that promotes higher than normal average current inthe motor to provide a higher than normal starting torque. Again, insome circumstances this will be sufficient to dislodge the blockage. Instep 125, the CPU again monitors the pump speed and if this is above thethreshold then the pump operation continues as normal. However, if theblockage has not yet dislodged and the pump speed is below the thresholdthen the controller 50 will stop the motor again, and step the motorbackwards, step 126. As the motor of the pump can be operated as astepper motor, the motor can be operated backwards in a step-wisefashion in a manner known to those skilled in the art. Preferably, themotor will be stepped back 180°, although any other degrees of steppingcould be implemented, step 126. In step 127, the controller restarts themotor of the pump 8 using a normal excitation, or an elevated excitationas an option. Again, the backwards stepping and restarting might besufficient to dislodge the blockage.

In step 128, the CPU again monitors the motor speed, and if it is abovethe threshold then operation continues as normal. However if not, it isdetermined that the blockage still exists. In step 129, in this case theCPU 51 stops the pump and then restarts it again using a normal, oroptionally elevated excitation. Once more, the CPU monitors the pumpcurrent and determines if the blockage still exists, step 130. If thepump speed is below the threshold, then the blockage is determined asstill existing. In this case the process will stop and the CPU will stopthe pump and stop operation of the washing machine and provide a warningto indicate that there is a fault that requires a technician, step 131.

It will be appreciated that it may not be necessary to implement all thesteps of this process in a regime for overcoming a blockage. The CPU 51might be programmed to only carry out one or a selection of the steps.Alternatively, additional steps might be added, or variations tooperation of the pump in order to attempt to dislodge a blockage.

As shown in FIG. 6, the pump housing cap 42 comprises a leak flowrecirculation tube 43 d. This tube 43 d provides a conduit between thepump housing 20 and volute to provide fluid communication with theinside of the bowl 6. The leak flow recirculation tube 43 d is providedto reduce unseating forces that can be present on the flapper valve 27during operation. Water dynamic and static forces in the housing 20during operation can upset the seating of the valve 27, such that itdoes not seal completely when it is abutting against either the drain 22or recirculation outlets 21, therefore allowing undesirable leakage intoeither the recirculation 21 or drain 22 conduits. For example, if duringa drain cycle the flapper valve 27 has not seated properly to fully sealoff the recirculation opening 21, drain water can flow through therecirculation conduit 11 and spill on to the clothes within the bowl 6or during the spin cycle be shaken on to the cabinet/wrapper 1 interiorand down to the floor. The leak flow recirculation tube 43 d addressesthis problem by equalising the pressure outside the pump housing 20 withthe pressure in the recirculation conduit 11 such that water level inthe conduit 11 does not rise substantially above the water level in thewashing machine bowl 6.

The leak flow recirculation tube 43 d provides fluid communicationbetween the interior of the recirculation outlet 21 and the outside ofthe housing. As shown in FIG. 6, the leak flow tube 43 d vents into thevolute defined by the flower shaped hood 45 and the cap 42 wall 43.Other alternative are possible. For example, the leak flow tube couldvent directly into the bowl 6, or could vent directly into the capaperture 43 a. The leak flow tube 43 d can vent anywhere where there isa lower pressure that provides equalisation. In the present embodiment,as described earlier, the coercing of the water flow from the aperture43 a to the leak flow tube 43 d creates a lower pressure above the leakflow tube which enables equalisation. This equalises the pressurebetween the volute and the interior of the recirculation outlet.

In a preferred embodiment the leak flow recirculation tube 43 d alignsand corresponds with an aperture in the recirculation outlet 21, whichallows for pressure equalisation directly between the recirculationoutlet 21 and the volute 43 b. This equalisation provides forapproximate pressure equalisation between the water in the bowl 6 andthe water in the recirculation outlet 21 and conduit 11 when the flappervalve 27 closes of the outlet 21. The leak flow recirculation tube 43 dis in fluid communication with the volute which itself is in fluidcommunication with the bowl 6 via the gap created between the volutewall and the hood and also the “V” notches 42 d and 42 c in the volutewall. There is some pressure drop between the bowl itself and thevolute, such that the leak flow recirculation tube does not quiteequalise the pressure of the recirculation outlet 21/conduit 11 with thebowl 6 pressure, although it approximately equalises the pressure inboth. The pressure differential is minimal which means that the water inthe conduit 11 is prevented from rising above the water level in thebowl. The pressure in the cap/hood cavity is lower than that at theequivalent height in the bowl itself.

Further, the leak flow recirculation tube provides for reduction inflapper valve 27 unseating forces to reduce leakage and improve sealing.This is because it will lower the height of the water in therecirculation tube and hence the pressure acting on the back of theflapper trying to unseat it. The leak flow recirculation tube 43 d canalso be flushed when the impeller stops. The head of water in therecirculation pipe flows back and up through the leak flow recirculationpipe 43 d to remove lint and other particles, as shown by the arrow inFIG. 15. At the end of the recirculation phase, when the impeller stopsrotating, water that was in the recirculation hose returns throughgravity back into the pump housing 20. The majority of the water flow isdirectly through the recirculation outlet 21 but a portion will beflushed up through the leak flow recirculation tube 43 along the hoodbulb 47 and some will be flushed through the aperture 48 in the bowl.

In another possible embodiment of the invention, a second set of vanesare formed on the under-side of the impeller 36 as shown in FIG. 13. Theimpeller as shown in FIG. 13 includes a generally circular body portion130 which comprises a top surface 131 and a bottom surface 132. The topsurface comprises preferably four impeller blades or vanes 133 a-133 d amoulded bearing cavity 134 so that the impeller can be installed on anaxle of the rotor. The main body is partially concave upwards. Thebottom surface of the impeller comprises a recess 135 and eight impellervanes or blades 136 a-136 h. The impeller blades 133 a-133 d transfer ormove water upon rotation of the impeller. This provides for transfer ofwater to the drain or recirculation outlets as required based on thedirection. If the impeller rotates clockwise the water will be moved andforced into the drain outlet 22 and if the impeller movescounter-clockwise the water will be moved into the recirculation outlet21.

The bottom surface is convex in shape and is commensurate with theconcave shape of the bearing 134. This allows for the impeller to rotateon the bearing with a small degree of tolerance. However foreign objectsand debris may become lodged between the bottom surface of the impeller132 and the top concave surface of the bearing 134. This can affect theoperation of the impeller and the pump. During operation the vanescreate a whirlpool or vortex in the area between the impeller and thebearing 134. There is no inlet to this, so the fluid will flow radiallyrather than axially. If there is debris in this whirlpool, for example asand particle, that is denser than water, it will be thrown outwards dueto the whirlpool effect or vortex as it is heavier than thecorresponding water particle that will take its place. The vortexcreated effectively emits particles from between the impeller and thebearing through a centrifugal action. This improves movement of theimpeller if there is a particle lodged between the two surfaces andreduces shaft, seal and bearing wear, thereby prolonging the pump life.The centrifugal action bought about by the rotation of these vanes emitsforeign objects from between the impeller and the rotor cap 34 andreduces shaft seal and bearing wear, thereby prolonging the pump life.

The vanes 136 a-136 i can be changed in number, height and spacing toimprove the removal of debris as required. The vanes a configured tocreate a suitable drag to effect a vortex.

Referring to FIGS. 6 and 14 a, 14 c the flower shaped walls 43 extendingfrom the top of the housing 42 to produce the volute, includes V shapednotches 42 c, 42 d in either end. These notches allow the inflow ofwater to prime the pump prior to the water level reaching the height ofthe flower shaped wall 43. The flower shaped wall 43 in combination withthe corresponding flower shaped hood 45 provides a filtering mechanism.The moulded flower shape of the hood 45 corresponds with that of thevolute wall 43 although it is marginally wider and comprises a lip 49that extends partially over the wall 43. This provides a flower shapedgap 140 (see FIGS. 14 a, 14 c) around the perimeter of the volute wall.

This arrangement allows water to flow into and out of the volute (seearrow 144 in FIG. 14 c and also FIG. 15). However, the shape of theperimeter opening 140 formed by the hood 48 and the volute wall 43limits the size of foreign particles that can enter the volute. Forexample referring to the elongated foreign article 141, an article thatis too long will not fit in the gap as the curved walls limit themaximum straight length 143 provided in the gap. This in turn limits thelength/size of particles that can enter the volute between the hood45/wall 43 gap 140. This provides for some filtering of the water.

FIG. 14 a shows just one possible embodiment of the wall that ispreferred. Any suitable irregular shape of the volute wall could beprovided. Another example is shown in FIG. 14 b, which is triangular inshape. What is required is having an outer exterior profile or shape ofwall 43 that overall is substantially non-planar with a correspondinglip on the hood 45 with a corresponding profiled inner surface facingthe exterior profiled wall 43. This could be provided by curved walls,angular walls or any other suitable geometry. The irregular curves orangles are arranged such that the maximum length e.g. 143 in the gapbetween the volute wall and the hood lip 49 is small enough to preventparticles of a greater length entering through the gap into the volute.This maximum length can be designed as any considered suitable for theparticular application. It will be appreciated that if the maximumlength in the gap is made very small, this will prevent most particlesfrom entering, but may also restrict water flow through the gap and intothe volute to an undesirable level. Making the maximum length in the gaptoo long will allow more water in, but will also may let throughparticles of an unacceptable size.

It will be appreciated that it is the profile of the space or gap 140that provides a filtering effect, which is achieved by the combinationof the profile or shape of the inside surface of the lip 49 on the hood45 and the profiled exterior shape of the wall 43. The interior shape ofthe volute wall and the exterior shape of the hood and lip are notcritical.

The profiled bulb 47 is provided to remove air bubbles from the pumpwhich may reduce performance and give false ventilation messages to thecontroller 50. If there is air in the pump 8 that cannot escape, nowater can enter as there is air in the way, so no water can be pumped.If the pump empties of water naturally (e.g. dries up over time), theair must be able to escape when new water comes in. If it cannot, airbubbles will form. For example, when the air is stirred up in to thewater volume, these individual bubbles combine to form a large bubble.If this bubble sits on top of the impeller and gets caught in thevortex, it cannot escape. The pump cannot pump water, even if more waterenters the system, say through a rinse cycle. Ventilation sensing sensesthe current drop when the pump begins pumping air. If this air happensto be an air bubble when there is water left in the pump, the controllerwill incorrectly detect ventilation and stop pumping. Any such airbubbles in the pump rise through the opening and into the bulb 47 thatis situated above the water level in the pump. The aperture 48 in thebulb 47 allows for any air bubble in the bulb to vent through into thewashing machine bowl 1. It also allows the bubble to rise before itreaches the impeller or once it breaks free. The profile bulb 47 alsoallows lint streams to escape from the leak flow recirculation tube 43 dby providing extra clearance between the top of the conduit 43 d andhood 45. That is, if lint or other foreign objects form into a ball orotherwise, they can be accommodated by the extra volume provided by thebulb 47. This allows the bigger objects to reside temporarily in thebulb and subsequently escape the from hood, rather than getting jammedwhich would happen if the hood were flat.

A washing machine can incorporate one or a combination of two or more ofthe features described above to improve the operation of the washingmachine.

1. A washing machine comprising: a bowl adapted to hold water, an inletwith a valve adapted for connection to a water supply, the inlet andvalve allowing controlled introduction of water into the bowl when theinlet is connected to a water supply, a variable speed pump adapted torecirculate water within the bowl, a sensor adapted to measure one ormore parameters indicative of current drawn by the pump duringoperation, a controller apparatus operatively connected to said pump andsaid sensor, and configured to: (a) compare said measure of said currentdrawn by said pump during operation to a threshold current, said currentbeing below said threshold indicative of when said pump is ventilating,(b) increment a first timer when said pump is pumping, (c) increment asecond timer when said pump is ventilating, (d) determine a ratiobetween said first and second timers, and (e) operate said valve toprevent the flow of water into said bowl when said ratio between saidfirst and second timers exceeds a timer threshold.
 2. A washing machineas claimed in claim 1, wherein said timer threshold is determine bydesired total wash-time and water economy.
 3. A washing machine asclaimed in claim 1, wherein said timer threshold is less than 100%.
 4. Amethod of controlling a washing machine having a bowl to hold water, aninlet valve for allowing the controlled introduction of water to thewash bowl, a variable speed pump adapted to recirculate water within thebowl, a sensor adapted to measure one or more parameters indicative ofcurrent drawn by the pump during operation and a controller connected tosaid pump and said sensor, comprising the steps of (a) compare saidmeasure of said current drawn by said pump during operation to athreshold current, said current being below said threshold indicative ofwhen said pump is ventilating, (b) increment a first timer when saidpump is pumping, (c) increment a second timer when said pump isventilating, (d) determine a ratio between said first and second timers,and (e) operate said valve to prevent the flow of water into said bowlwhen said ratio between said ratio between said first and second timersexceeds a timer threshold.
 5. A method of controlling a washing machineas claimed in claim 4, wherein said timer threshold is determined bydesired total wash-time and water economy.
 6. A method of controlling awashing machine as claimed in claim 4, wherein said timer threshold isless than 100%.